PSI - Issue 14

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Anigani Sudarshan Reddy et al. / Procedia Structural Integrity 14 (2019) 449–466 Author name / Structural Integrity Procedia 00 (2018) 000–000

Figure 18 represents 0.2% YS and UTS to be 415 MPa and 630 MPa respectively after failure of hybrid. Figure 19 represents the micro tensile specimen of the hybrid (CoCrMo on FSX414) after failure. It can be seen that the specimen has failed on the cast FSX414 side indicating a sound weld joint between DMLS CoCrMo and FSX414.

0 100 200 300 400 500 600 700

Strength (MPa)

0.2% YS

UTS

Fig. 18. Small tensile specimen of hybrid (DMLS CoCrMo on FSX414) after failure.

FSX-414 side

Welded region

Fig .19. Mechanical properties of Hybrid (DMLS CoCrMo and FSX414) in the heat treated condition

4. Conclusions This study presents a comparison of mechanical properties of small scale and regular tensile specimens in the as printed and heat treated condition for monolithic DMLS materials (IN718, CoCrMo, Maraging steel, SS316L, Ti6Al4V) and hybrids (DMLS SS316L on X20Cr13, DMLS CoCrMo on Cast FSX414) along the build direction. The starting powders of all alloys shows spherical morphology with average particle size of 33-38 µm and particle size distribution of 11-86 µm. A dense structure (>99.5%) was produced without any Hot Isostatic Pressing (HIP) by using optimized process parameters. The microstructure after heat treatments results in partial recrystallization with elongated grains for IN718, equiaxed grains with  40 µm grain size for CoCrMo, no changes for Maraging steel, columnar grains structure for SS316L and characteristic biphasic  +  phase for Ti6Al4V. The microstructure of hybrids is similar to monolithic DMLS in the DMLS regions. The tensile properties of small scale specimens in the as printed condition are in close conformance to their regular ASTM test results with < 5% difference in all values 0.2% YS, UTS and %elongation for CoCrMo, Maraging steel and SS316L. Only IN718 and Ti64 recorded a 10% difference with the small scale test specimens recording a lower value as compared to the regular specimens in the as printed condition. However, after heat treatment, all the alloys show similar tensile properties with < 2% difference between the small scale and regular specimens. The tensile